Solvent refining of mineral oil



Patented Dec. 7, 1937 UNITED STATES PATENT SOLVENT EEFINING F IVHNERAL OIL No Drawing. Application August 10, 1935, Serial No. 35,632

4 Claims.

This invention relates to refining hydrocarbon oil and more particularly to refining mineral oil by treatment with a selective solvent liquid.

The invention contemplates a process for the 5 treatment of mineral oil with a solvent comprising beta trichlorethane for the purpose of effecting removal of solidparaffin hydrocarbons, as well as low viscosity index hydrocarbons to thereby produce lubricatingfoil of low pour test and high viscosity index.

The solvent of this invention has the formula CHzClCHClz and is a compound having a boiling point of around 237 F. This compound provides a satisfactory dewaxing solvent for the dewaxing of wax bearing mineral oil and may also be used in conjunction with other suitable solvent liquids such as furfural to effect separation between relatively low and relatively high viscosity. index constituents of the oil.

. The particular advantage of the beta comthe oil undergoing treatment, and the solvent reactsto some extent with the oil as evidenced by darkening in color of the oil.

It has been found however that beta trichlorethane is quite stable during distillation and does not cause abnormal darkening of the oil, such as occurs when using trichlor ethylene for example. This high degree of stability is of advantage when using the solvent in conjunction with other solvents, such as furfural. For example, when oil is extracted with furfural in the presence of beta trichlorethane there is no apparent reaction between the chlorinated compound and the furfural.

This solvent also possesses the further advantages of being non-inflammable and non-corroslve.

In order to more fully describe the invention, reference will now be made to the following example in which a wax bearing distillate derived from Mid-Continent crude, having a viscosity of around 60 Saybolt universal seconds at 210 F. and a pour test of around 90 F. was dewaxed with beta trichlorethane.

In dewaxing this oil, one part of oil was mixed with about four parts of the solvent liquid and the resulting mixture was chilled to a temperature of 0 F. to precipitate the waxing constituents. While maintained at this low temperature, the cold mixture was filtered to separate and remove the precipitated wax constituents.

The solvent liquid was removed from the resulting filtrate by distillation, and there was obtained a dewaxed oil amounting to about of the original wax bearing distillate. This dewaxed oil had apour test of 5 F.

While the foregoing example has to do with the employment of this solvent in the dewaxing of wax bearing mineral oil, it is contemplated however that it may also be advantageously used as an auxiliary solvent to facilitate removal of relatively low viscosity index hydrocarbons, as well as other undesirable constituents. Thus it has been found that a mixture of furfural and beta trichlorethane provides a satisfactory solvent mixture for the solvent refining of parafiin base residuum in order to produce high vis cosity index oil having a relatively low carbon residue content.

In order to illustrate the utility of this solvent as an auxiliary solvent, the following example will now be referred to, in which a dewaxed parafiln residuum obtained from Mid-Continent crude was extracted with a mixture composed of equal parts of furfural and beta trichlorethane.

In carrying out this experiment, one part of the dewaxed parafiin residuum was mixed with two parts of the solvent mixture and the treatment carried out in a single batch extraction at a temperature of 77 F. After thorough agitation, the mixture was allowed to separate into extract and rafiinate phases. These phases were separated and the solvent liquid recovered therefrom by distillation. The resulting raifinate oil amounted to about 54% by volume of the residuum and the tests on this rafiinate oil, as com pared with the residuum before extraction, were as follows:

Residuum Raflinate Gravity A. P. I 17.8 21.8 Viscosity S. U./2l0 159 137 Viscosity index 56 73 Carbon residue, percent 6. 9 l. 9

advantageously be carried out in conjunction with each other. Thus, in the case of a wax bearing mineral oil, the oil may be mixed with the trichlorethane in proportions sufficient to effect dewaxing. Following the dewaxing step,

the dewaxed solution, with or without partial removal of the dewaxing solvent, may then be extracted with furfural' or some other suitable selective solvent liquid. It may be necessary to modify the dewaxed solution prior to the extracting step, in which case a portion of the de-' waxing solvent may be removed by distillation, leaving a mixture of dewaxed oil and trichlorethane, which when mixed; with the' proper amount of furfural or other selective solvent liquid will provide a solvent mixture having the desired degree of selective action as between relatively low and relatively high viscosity index constituents.

In carrying out the separating step the mixture of dewaxed oil, trichlorethane and furfural may be maintained at any desired extraction temperature, as for example, ranging from about to 225 F., in order to effect separation of the mixture intoextract and rafiinate phases.

It is contemplated that this extraction step may be carried out either bymultiple batch or by continuous countercurrent application of the solvent to the oil. f r

The temperature as Well as the ratio of solvent to oil employed in carrying out the dewaxing and extraction treatments may be varied for the purpose of. effecting the particular degree of refining desired, and this will also depend to some extent upo-n the nature of the oil undergoing treatment;

The invention is not necessarily restricted to the treatment of distillate lubricating oil fractions but is equally adapted to thetreatment of. residual fractions. It may also be adapted to the treatment and purification of fractions other than lubricating oil, for example, naptha and kerosene. 7

Obviously, many modifications and variations of the invention as hereinbefore set forth maybe made without departing from. the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim,

1. The method of separating hydrocarbon oil containing high viscosity and low viscosity index constituents intofractions which are respectively rich in high viscosity index and low viscosity index constituents, which comprises extracting the oil with furfural in the presence of beta trichlorethane, forming an extract phase containing low viscosity index constituents dissolved in solvent liquid and a raffinate phase comprising relatively high viscosity index constituents, and separating the two phases.

2. The method of refining residual lubricating oil stock to remove low viscosity index constituents as well as asphaltic constituents which comprise extracting the oil with furfural in the presence of beta trichlorethane, forming an extract phase containing low viscosity index constituents and asphaltic constituents dissolved in the bulk of the solvent liquid mixture, and a rafiinate phase comprising relatively high viscosity index constituents, and separating the two phases.

3. The method of manufacturing high viscosity index oil of low pour test from wax-bearing mineral oil which comprises removing the wax and forming a mixture of dewaxed oil and beta-trichlorethane, extracting said mixture with furfural, forming an extract phase con taining low viscosity index constituents dissolved in the main bodyof solvent liquid and a raffinate phase comprising relatively high viscosity index constituents mixed with some of the solvent liquid, and separating the two phases.

4. The method of manufacturing high viscosity index oil from mineral lubricating oil which comprises forming a mixture of dewaxed oil and beta-trichlorethane, extracting said mixcosity index constituents mixed with some of the solvent liquid, and separating the two phases.

JAMES H. GRAHAIWE. 

